In the treatment of exuding wounds there is a need for an absorbent dressing being capable of adapting to the conformation of the individual wound. This may be done by using fibre dressings or hydrogels.
Wound care devices comprising fibres may be based on polysaccharide fibres, which are usually water insoluble, but water absorbing. They are in general based on alginate or CMC. Wound care products such as dressings or fillers based on alginate or CMC, may be able to absorb up to 15-25 g exudate/gram product, with limited swellablity and gellability. These fibre dressings/fillers are normally supplied as sterile.
The use of fibres often suffers from the drawback of a limited absorption and/or lack of cohesion, leading to difficulties with respect to removing the fibre product from the wound as the product does not constitute a cohesive part.
Methods of preparing alginate fibres are well known. Normally sodium alginate is completely converted into insoluble calcium alginate fibres. Methods for enhancing the solubility of alginate fibres are also well known. International Patent Application No. WO 94/17227 discloses a method for preparing highly absorbent alginate fibres by conversion of calcium alginate fibres into alginic acid fibres.
In International Patent Application No. WO 94/16746 is disclosed a process of preparing carboxy methyl cellulose fibres which are gellable, but still coherent enough to be removed from a wound in one piece.
European Patent Application No. 627 225 discloses a method for preparing a superabsorbent chitosan powder, being capable of absorbing liquid many times it own weight by forming a transparent gel. This is done by treating the powderous chitosan with an acid, preferably a hydroxy carbon acid like lactic acid or hydroxy butylic acid. The resulting powder is capable of absorbing high amounts of water by forming a gel.
The acid-modified chitosan disclosed in EP 627 225 A2 is suitable for use as a superabsorbent in diapers and like products, in which the powdered material will be encapsulated and little or no coherence is demanded. However, the reference is silent with respect to preparation of highly coherent material, for use in e.g. wound care products.
Published Japanese Patent Application No. JP 9-169654-A discloses a method for preparing partly deacetylated chitin fibres for wound care. The preferred chitin material has a deacetylation degree of max. 90%, preferably 40-60%. The material is not used as an absorbent, but as a haemostatic agent for stopping bleeding wounds.
In European Patent Application No. 171 254 is disclosed chitin fibres being treated in an aqueous solution with acid and elevated temperature. The fibres remain their structure due to the fact that chitin is not soluble in an acidic aqueous solution.
Contrary to chitin, chitosan is soluble in an acidic aqueous solution.
International Patent Application No. 97/29132 discloses chitosan being dissolved in a weak acidic aqueous solution. The chitosan is treated with a carboxylic acid polyanhydride as a cross-linking agent. The resulting hydrogel may subsequently be processed into powders or fibres.
Thus, there still is a need for a wound care device comprising a material being capable of absorbing large amount of liquid by gelling, having a three-dimensional structure in the form of fibres, and having a high degree of cohesion after absorption. The need is fulfilled by the wound care device of the present invention.